Mid-range vinylidene content polyisobutylene polymer product produced by liquid phase polymerization process

ABSTRACT

A mid-range vinylidene content PIB polymer composition made by a liquid phase polymerization process conducted in a loop reactor at a temperature of at least 60° F. using a BF 3 /methanol catalyst complex and a contact time of no more than 4 minutes. At least about 90% of the PIB molecules present in the product comprise alpha or beta position isomers. The vinylidene (alpha) isomer content of the product may range from 20% to 70% thereof, and the content of tetra-substituted internal double bonds is very low, advantageously no more than about 10%, preferably less than about 5% and ideally less than about 1-2%.

CROSS REFERENCES TO RELATED APPLICATION

This application is a continuation of application Ser. No. 10/968,630filed Oct. 19, 2004 (now U. S. Pat. No. 7,056,990) from which prioritybenefits are claimed pursuant to 35 U.S.C. § 120. application Ser. No.10/968,630 in turn is a continuation of and claims priority benefitspursuant to 35 U.S.C. § 120 from application Ser. No. 10/102,279 filedMar. 19, 2002 (now U. S. Pat. No. 7,037,999), which in turn claimspriority benefits pursuant to 35 U.S.C. § 119(e) from provisionalapplication Ser. No. 60/279,305 filed Mar. 28, 2001. Said applicationSer. No. 10/968,630 also is a continuation of and claims prioritybenefits pursuant to 35 U.S.C. § 120 from application Ser. No.10/208,234 filed Jul. 30, 2002 (now U. S. Pat. No. 6,884,858), and whichin turn is a continuation of and claims priority pursuant to 35 U.S.C. §120 from application Ser. No. 09/665,084 filed Sep. 20, 2000 (now U. S.Pat. No. 6,525,149), which again in turn is a continuation-in-part ofand claims priority pursuant to 35 U.S.C. § 120 from utility applicationSer. No. 09/515,790 filed Feb. 29, 2000 (now U.S. Pat. No. 6,562,913)and which again in turn claims priority benefits pursuant to 35 U.S.C. §119(e) from provisional application Ser. No. 60/160,357, filed Oct. 19,1999. The entireties of each of the disclosures of each of said priorapplications are hereby specifically incorporated herein by thisreference thereto.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the preparation of polyisobutylene(PIB). In particular the present invention relates to the preparation ofa mid-range vinylidene content PIB composition. In this regard, theinvention provides a novel liquid phase process for the polymerizationof isobutylene to prepare a mid-range vinylidene content PIB compositionusing a modified BF₃ catalyst. The invention also provides a novelcomposition of matter comprising a mid-range vinylidene content PIBcomposition.

2. The Prior Art Background

The polymerization of isobutylene using Friedel-Crafts type catalysts,including BF₃, is a generally known procedure which is disclosed, forexample, in “HIGH POLYMERS”, Vol. XXIV (J. Wiley & Sons, Inc., New York,1971), pp. 713 ff. The degree of polymerization of the products obtainedvaries according to which of a number of known polymerization techniquesis used. In this latter connection, it is to be understood that, ingeneral, the molecular weight of the polymeric product is directlyrelated to the degree of polymerization.

It is also known that PIB may be manufactured in at least two differentmajor grades—i.e., regular and high vinylidene. Conventionally, thesetwo product grades have been made by different processes, but both oftenand commonly use a diluted isobutylene feedstock in which theisobutylene concentration may range from 40-60% by weight. More recentlyit has been noted that at least the high vinylidene PIB may be producedusing a concentrated feedstock having an isobutylene content of 90% byweight or more. Non-reactive hydrocarbons, such as isobutane, n-butaneand/or other lower alkanes commonly present in petroleum fractions, mayalso be included in the feedstock as diluents. The feedstock often mayalso contain small quantities of other unsaturated hydrocarbons such as1-butene and 2-butene.

Regular grade PIB may range in molecular weight from 500 to 1,000,000 orhigher, and is generally prepared in a batch process at low temperature,sometimes as low as −50 to −70 EC. AlCl₃, RAlCl₂ or R₂AlCl are used ascatalysts. The catalyst is generally not totally removed from the finalPIB product due to processing peculiarities. Molecular weight may becontrolled by temperature since the molecular weight of the productvaries inversely with temperature. That is to say, higher temperaturesgive lower molecular weights. Reaction times are often in the order ofhours. The desired polymeric product has a single double bond permolecule, and the double bonds are mostly internal. Generally speaking,at least about 90% of the double bonds are internal and less than 10% ofthe double bonds are in a terminal position. Even though the formationof terminal double bonds is believed to be kinetically favored, the longreaction times and the fact that the catalyst is not totally removed,both favor the rearrangement of the molecule so that the morethermodynamically favored internal double bond isomers are formed.Regular PIB may be used as a viscosity modifier, particularly in lubeoils, as a thickener, and as a tackifier for plastic films andadhesives. PIB can also be functionalized to produce intermediates forthe manufacture of detergents and dispersants for fuels and lube oils.

High vinylidene PIB, a relatively new product in the marketplace, ischaracterized by a large percentage of terminal double bonds, typicallygreater than 70% and preferentially greater than 80%. This provides amuch more reactive product, compared to regular PIB, and hence thisproduct is also referred to as highly reactive PIB. The terms highlyreactive (HR-PIB) and high vinylidene (HV-PIB) are synonymous. The basicprocesses for producing HV-PIB all include a reactor system, employingBF₃ and/or modified BF₃ catalysts, such that the reaction time can beclosely controlled and the catalyst can be immediately neutralized oncethe desired product has been formed. Since formation of the terminaldouble is kinetically favored, short reactions times favor highvinylidene levels. The reaction is quenched, usually with an aqueousbase solution, such as, for example, NH₄OH, before significantisomerization to internal double bonds can take place. Molecular weightsare relatively low. As used in this application, the terminology“relatively low” refers to a number average molecular weight (M_(N))which is less than about 10,000. HV-PIB having an M_(N) of about950-1050 is the most common product. Conversions, based on isobutylene,are kept at 75-85%, since attempting to drive the reaction to higherconversions reduces the vinylidene content through isomerization. PriorU.S. Pat. No. 4,152,499 dated May 1, 1979, U.S. Pat. No. 4,605,808 datedAug. 12, 1986, U.S. Pat. No. 5,068,490 dated Nov. 26, 1991, U.S. Pat.No. 5,191,044 dated Mar. 2, 1993, U.S. Pat. No. 5,286,823 dated Jun. 22,1992, U.S. Pat. No. 5,408,018 dated Apr. 18, 1995 and U.S. Pat. No.5,962,604 dated Oct. 5, 1999 are directed to related subject matter.

U.S. Pat. No. 4,152,499 describes a process for the preparation of PIBsfrom isobutylene under a blanket of gaseous BF₃ acting as apolymerization catalyst. The process results in the production of a PIBwherein 60 to 90% of the double bonds are in a terminal (vinylidene)position.

U.S. Pat. No. 4,605,808 discloses a process for preparing PIB wherein acatalyst consisting of a complex of BF₃ and an alcohol is employed. Itis suggested that the use of such a catalyst complex enables moreeffective control of the reaction parameters. Reaction contact times ofat least 8 minutes are required to obtain a PIB product wherein at leastabout 70% of the double bonds are in a terminal position.

U.S. Pat. No. 5,191,044 discloses a PIB production process requiringcareful pretreatment of a BF₃/alcohol complex to insure that all freeBF₃ is absent from the reactor. The complex must contain a surplus ofthe alcohol complexing agent in order to obtain a product wherein atleast about 70% of the double bonds are in a terminal position. The onlyreaction time exemplified is 10 minutes, and the reaction is carried outat temperatures below 0 EC.

In addition to close control of reaction time, the key to obtaining highvinylidene levels seems to be control of catalyst reactivity. This hasbeen done in the past by complexing BF₃ with various oxygenatesincluding sec-butanol and MTBE. One theory is that these complexes areactually less reactive than BF₃ itself, disproportionately slowing theisomerization reaction and thus allowing for greater differentiationbetween the vinylidene forming reaction (polymerization) and theisomerization reaction rates. Mechanisms have also been proposed thatsuggest the BF₃ complexes are non-protonated and thus are not capable ofisomerizing the terminal double bond. This further suggests that water(which can preferentially protonate BF₃) must generally be excluded fromthese reaction systems. In fact, prior publications describingpreparation of PIB using BF₃ complexes teach low water feed (less than20 ppm) is critical to formation of the high vinylidene product.

HV-PIB is increasingly replacing regular grade PIB for the manufactureof intermediates, not only because of higher reactivity, but alsobecause of developing requirements for “chloride free” materials in thefinal product applications. Important PIB derivatives are PIB amines,PIB alkylates and PIB maleic anhydride adducts.

PIB amines can be produced using a variety of procedures involvingdifferent PIB intermediates which provide a reactive site for subsequentamination. These intermediates may include, for example, epoxides,halides, maleic anhydride adducts, and carbonyl derivatives.

Reference to HV-PIB as “highly reactive” is relative to regular gradePIB. HV-PIB is still not, in absolute terms, highly reactive towardformation of some of these intermediates. Other classes of compounds,polyethers for example, can be much more reactive in the formation ofamines and amine intermediates. Amines derived from polyethers are knownas polyether amines (PEA=s) and are competitive products to PIB amines.

The use of HV-PIB as an alklylating agent for phenolic compounds, istriggered by the higher reactivity and higher yields achievable withHV-PIB. These very long chain alkyl phenols are good hydrophobes forsurfactants and similar products.

The largest volume PIB derivatives are the PIB-maleic anhydride reactionproducts. HV-PIB is reacted with maleic anhydride through the doublebond giving a product with anhydride functionality. This functionalityprovides reactivity for the formation of amides and other carboxylatederivatives. These products are the basis for most of the lube oildetergents and dispersants manufactured today. As mentioned above,PIB-maleic anhydride products can also be used as intermediates in themanufacture of PIB amine fuel additives.

More recently, a novel more valuable process for the efficient andeconomical production of HV-PIB has been developed. This new process isdescribed in U.S. Pat. No. 6,562,913 (hereinafter “the '913 patent”),which issued on May, 13, 2003 and is commonly owned with the presentapplication. The entirety of the disclosure of the '913 patent is herebyincorporated into the present application by this specific referencethereto.

The '913 patent relates to a HV-PIB production process wherein thepolymerization reaction takes place at higher temperatures and at lowerreaction times than had previously been thought possible. In particular,the '913 patent describes a liquid phase polymerization process forpreparing low molecular weight, highly reactive polyisobutylene.Generally speaking, the process of the '913 patent may involve cationicpolymerization. However, under some conditions the polymerizationreaction may be covalent. Particularly the latter may be true when etheris used as a complexing agent. In accordance with the disclosure of the'913 patent, the process includes the provision of a feedstockcomprising isobutylene and a catalyst composition comprising a complexof BF₃ and a complexing agent. The feedstock and the catalystcomposition are introduced either separately or as a single mixed streaminto a residual reaction mixture in a reaction zone. The residualreaction mixture, the feedstock and the catalyst composition are thenintimately intermixed to present an intimately intermixed reactionadmixture in the reaction zone. The reaction admixture is maintained inits intimately intermixed condition and kept at a temperature of atleast about 0 EC. while the same is in said reaction zone, whereby theisobutylene in the reaction admixture is caused to undergopolymerization to form a polyisobutylene product. A product streamcomprising a low molecular weight, highly reactive polyisobutylene isthen withdrawn from the reaction zone. The introduction of the feedstockinto said reaction zone and the withdrawal of the product stream fromthe reaction zone are controlled such that the residence time of theisobutylene undergoing polymerization in the reaction zone is no greaterthan about 4 minutes. In accordance with the '913 patent, it is possibleto conduct the reaction so that the residence time is no greater thanabout 3 minutes, no greater than about 2 minutes, no greater than about1 minute, and ideally, even less than 1 minute.

In accordance with the concepts and principles disclosed in the '913patent, the process may be conducted in a manner such that thepolyisobutylene thus produced has an M_(N) in the range of from about350 to about 5000, in the range of from about 600 to about 4000, in therange of from about 700 to about 3000, in the range of from about 800 toabout 2000, and ideally in the range of from about 950 to about 1050.Moreover, it is possible to so control the process that a particularM_(N), such as for example, an M_(N) of about 1000, may be achieved.

The '913 patent thus discloses a process which may be controlledsufficiently to insure the production of a polyisobutylene producthaving a vinylidene content of at least about 70%. More preferably thePIB product may have a vinylidene content of at least about 80%. Infact, vinylidene content of at least about 90% may be easily achievedthrough the use of the teachings of the '913 patent.

As set forth in the '913 patent, the complexing agent used to complexwith the BF₃ catalyst may desirably be an alcohol, and preferably may bea primary alcohol. More preferably the complexing agent may comprise aC₁-C₈ primary alcohol and ideally may be methanol.

To achieve the most desired results in accordance with the teachings ofthe '913 patent, the molar ratio of BF₃ to complexing agent in thecomplex may range from approximately 0.5:1 to approximately 5:1.Preferably the molar ratio of BF₃ to complexing agent in the complex mayrange from approximately 0.5:1 to approximately 2:1. Even morepreferably the molar ratio of BF₃ to complexing agent in the complex mayrange from approximately 0.5:1 to approximately 1:1, and ideally, themolar ratio of BF₃ to complexing agent in the complex may beapproximately 1:1.

In further accord with the teachings of the '913 patent, it is preferredthat from about 0.1 to about 10 millimoles of BF₃ may be introduced intothe reaction admixture with the catalyst composition for each mole ofisobutylene introduced into the admixture in the feedstock. Even morepreferably, from about 0.5 to about 2 millimoles of BF₃ may beintroduced into the reaction admixture with said catalyst compositionfor each mole of isobutylene introduced into the admixture in thefeedstock.

When the teachings of the '913 patent are applied, a process is providedwhereby the polydispersity of the produced polyisobutylene may be nomore than about 2.0, and desirably may be no more than about 1.65.Ideally, the polydispersity may be in the range of from about 1.3 toabout 1.5.

In accordance with one preferred embodiment taught in the '913 patent,the reaction zone may comprise a loop reactor wherein the reactionadmixture is continuously recirculated at a first volumetric flow rate,and the feedstock and the catalyst composition may be continuouslyintroduced at a combined second volumetric flow rate. The ratio of thefirst volumetric flow rate to the second volumetric flow rate maydesirably range from about 20:1 to about 50:1, may preferably range fromabout 25:1 to about 40:1 and ideally may range from about 28:1 to about35:1. In order to achieve the preferred benefits of the loop reactor,the ratio of the first volumetric flow rate to the second volumetricflow rate may preferably be such that the concentrations of ingredientsin the reaction admixture remain essentially constant and/or such thatessentially isothermal conditions are established and maintained in thereaction admixture.

As described in the '913 patent, the feedstock and the catalystcomposition may be premixed and introduced into the reaction zonetogether as a single stream at the second volumetric flow rate.Alternatively, the feedstock and the catalyst composition may beintroduced into the reaction zone separately as two respective streams,the flow rates of which together add up to the second volumetric flowrate.

To achieve the ideal results described in the '913 patent, the reactorconfiguration, the properties of the reaction mixture, and the firstvolumetric flow rate may be such that turbulent flow is maintained inthe reaction zone. In particular, the system may be such that a Reynoldsnumber (Re) of at least about 2000 is achieved and maintained in thereaction zone. The system may also be such that a heat transfercoefficient (U) of at least about 50 Btu/min ft² EF. is achieved andmaintained in the reaction zone. To this end, the reactor may desirablybe the tube side of a shell-and-tube heat exchanger.

In further accordance with the concepts and principles of the novelprocess described in the '913 patent, the feed stock may generallycomprise at least about 30% by weight of isobutylene, with the remainderbeing non-reactive hydrocarbon diluents.

As mentioned above, high vinylidene PIB contains only a single doublebond in each molecule, and most of these are in the terminal (alpha)position. Typically, more than 70%, and preferentially more than 80%, ofthe double bonds are in the terminal (alpha) position. Generallyspeaking, in known high vinylidene PIB products, the remaining 20 to 30%of the double bonds are in the beta position (between the second andthird carbon atoms of the polymeric backbone). These beta positiondouble bonds may be either 1,1,2-trisubstituted or 1,2,2-trisubstituted.Almost no tetra-substituted isomers are present in the high vinylidenePIB made in accordance with the teachings of the '913 patent, so thatthe total of the alpha and beta isomers is essentially about 100%.

On the other hand, while regular (conventional) PIB also has only onedouble bond per molecule, only about 5-10% of those double bonds are inthe alpha position and only about 50% are in a beta position. Theremainder of the PIB isomers include double bonds that aretetra-substituted and internal to the polymer as a result ofisomerization reactions which occur during preparation. Because of thehigh level of the relatively non-reactive tetra-substituted olefincontent, these products are sometimes referred to as low reactive PIB.

In the past, the only known PIB compositions have been (1) the highlyreactive PIB containing essentially 100% alpha plus beta olefin isomers,with the vinylidene (alpha) isomer content being greater than 70%, and(2) the low reactive PIB in which the alpha plus beta isomer content isonly about 60% and the vinylidene (alpha) content is less than about10%.

SUMMARY OF THE INVENTION

The present invention provides a new, relatively low molecular weight,mid-range vinylidene content PIB polymer product and a process formaking the same. The alpha (vinylidene) position PIB isomers plus thebeta position PIB isomers present in the mid-range vinylidene contentPIB polymer product preferably comprise at least about 90% of the totalmolecules present in the product. Desirably, the alpha plus beta isomersmay comprise at least about 95% of the total molecules present in theproduct, and ideally the alpha plus beta isomers, may compriseessentially 100% of the total molecules present in the product.Generally, in accordance with the concepts and principles of theinvention, the vinylidene (alpha) isomer content of the product may beless than 70% thereof and may be as low as 20%. Conversely, the betaisomer content may range from about 30% to about 80% of the totalmolecules present in the product. In a mid-range vinylidene content PIBcomposition of the invention, the content of tetra-substituted internaldouble bonds is desirably very low, advantageously no more than about10%, preferably less than about 5% and ideally less than about 1-2% ofthe double bonds. The advantage of these products is that the overallreactivity thereof, for some applications, is still very high withoutthe need for high vinylidene content.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic illustration of a reactor in the form of aquadruple pass shell and tube heat exchanger which is useful forcarrying out the improved process and producing the improved mid-rangevinylidene of the invention; and

FIG. 2 is a schematic illustration of a reactor in the form of a doublepass shell and tube heat exchanger which is useful for carrying out theimproved process and producing the improved mid-range vinylidene of theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As mentioned above, new methodology for preparing high vinylidene PIBpolymers (>70% alpha position double bonds) is described in the '913patent, the entirety of the disclosure of which is incorporated hereinby reference. It has now been found, that in accordance with theconcepts and principles of the present invention, the process variablesdescribed in the '913 patent may be manipulated and/or adjusted so as toprovide the conditions needed for producing a mid-range vinylidenecontent PIB composition. In preparing the desired mid-range contentvinylidene PIB of the invention, wherein the vinylidene (alpha positiondouble bond) isomer content may be in the range of from about 20% toabout 70%, the process variables of the process disclosed in the '913patent may be manipulated as follows:

-   -   (1) a catalyst complexing agent (preferably methanol) to BF₃        ratio of 1.3:1 or less in the catalyst complex is desirably        employed resulting in reduced catalyst consumption because there        is a greater amount of BF₃ and a correspondingly lesser amount        of catalyst complexing agent in the catalyst complex;    -   (2) for any given M_(N) , a higher reaction temperature may be        employed. For an M_(N) of about 1050 or so, the temperature may        desirably roughly correspond to about 90 EF, whereas a typical        reaction temperature of 60 EF or so is desirable for producing        high vinylidene products;    -   (3) the reaction time may desirably be kept to a minimum,        preferably less than 4 minutes, and ideally less than one        minute; and    -   (4) the BF₃ to isobutylene feedstock ratio, reactor        configuration, residence time, catalyst concentration, Reynolds        number, U factor, volumetric flow rate range, feedstock        concentration, and M_(N) range may desirably be essentially the        same as disclosed in the '913 patent.

The polydispersity of the resulting mid-range vinylidene content PIBproduct produced as described above will tend to be narrower than thepolydispersity of the highly reactive PIB produced in accordance withthe process of the '913 patent because of lower catalyst consumption.Moreover, when the mid-range vinylidene content PIB product is preparedusing the conditions described above, the total amount of beta olefinisomers (1,1,2-trisubstituted or 1,2,2-trisubstituted) present in theresultant PIB polymer composition plus the amount of alpha isomerspresent in the resultant PIB polymer composition add up to almost 100%of the composition.

The mid-range vinylidene content PIB products produced employing theconcepts and principles of the present invention may generally be usedin place of the highly reactive PIB products described in the '913patent in many end-use applications. Although reaction speeds may beslightly to moderately lower than when the high vinylidene products areused, overall conversion rates are similar because the mid-rangevinylidene content PIB polymer composition comprises essentially 100%alpha olefin isomers plus beta olefin isomers, whereby the presence ofinternal double bond isomers is minimized.

It has been observed that the mid-range vinylidene content PIB olefincompositions of the present invention are efficiently reactive inend-use applications such as PIB alkylation onto aromatic rings,particularly phenolic compounds, as well as PIB amine derivatives andPIB-maleic anhydride reaction products. Tetra-substituted internaldouble bonds are not reactive in the formation of the above mentionedPIB derivatives, whereas beta position double bonds are.

Desirably the tetra-substituted internal double bond isomer content ofthe mid-range vinylidene content PIB products of the invention shouldgenerally be very low, typically no more than about 1-2%, so as tooptimize the performance of the product. However, it should be notedthat the amount of tetra-substituted internal double bond isomer thatmay be tolerated in a valuable commercial product may be as much as 5%or more.

As set forth above, the present invention provides an improved liquidphase process for the efficient and economical production of mid-rangevinylidene content PIB products. The invention also provides novelmid-range vinylidene content PIB products. In accordance with theinvention, an isobutylene containing feedstock stream is contacted in areaction zone with a catalyst which facilitates the polymerizationreaction. Appropriate reaction conditions as described above areprovided in the reaction zone. After an appropriate residence time, aPIB containing product stream is withdrawn from the reaction zone. Withthe foregoing in mind, the present invention provides an improved PIBproducing process which may be easily controlled and manipulated asdescribed above to efficiently and economically provide a relatively lowmolecular weight, mid-range vinylidene content PIB product.

The improved process of the present invention features the use of a BF₃catalyst which desirably may be complexed with a complexing agent thatappropriately alters the performance of the catalyst. Many otherpotentially useful catalysts are known to those of ordinary skill in therelated art field. In particular, many useful catalysts are described inthe prior patents referenced above. The complexing agent for thecatalyst, and in particular for the BF₃ catalyst, may be any compoundcontaining a lone pair of electrons, such as, for example, an alcohol,an ester or an amine. For purposes of the present invention, however,the complexing agent may preferably be an alcohol, desirably a primaryalcohol, even more desirably a C₁-C₈ primary alcohol and ideallymethanol.

As discussed above, for the purposes of the present invention, the molarratio of complexing agent to BF₃ in the catalyst composition shouldgenerally be about 1.3:1 or less, for example, 1.2:1 or less, 1.1:1 orless, 1:1 or less, and in fact, the catalyst composition may consist ofessentially uncomplexed BF₃ for some particularized applications. Indetermining the ratio, important considerations include avoidance offree BF₃ in the reactor and minimization of tetra substituted internaldouble bond isomers in the product. The temperature in the reaction zonemay generally and preferably be greater than 60 EF., and ideally may beabout 90 EF., although temperatures as low as 0 EF may be suitable wherea high molecular weight product is desired. The reactor residence timemay generally and preferably be less than 4 minutes and ideally may beless than one minute. With these parameters, it is possible to operatethe process so as to achieve efficiencies, economies and relatively lowmolecular weight, mid-range vinylidene content PIB products notpreviously thought to be available. In accordance with the presentinvention, the catalyst concentration and the BF₃/complexing agent ratiomay be manipulated as required to achieve the desired relatively lowmolecular weight, mid-range vinylidene content PIB products, usuallywith a reaction temperature greater than 60 EF. and a reactor residencetime of less than 4 minutes. Generally speaking, the amount of the BF₃catalyst introduced into the reaction zone should be within the range offrom about 0.1 to about 10 millimoles for each mole of isobutyleneintroduced into the reaction zone. Preferably, the BF₃ catalyst may beintroduced at a rate of about 0.5 to about 2 millimoles per mole ofisobutylene introduced in the feedstock.

The process itself includes steps resulting in the intimate mixing ofthe isobutylene containing reactant stream and the catalyst complexand/or removal of heat during the reaction. The intimate mixing maydesirably be accomplished by turbulent flow. Turbulent flow alsoenhances heat removal. These conditions separately or together permitthe higher operating temperatures (e.g. 60 EF.) and the shorter reactorresidence times (e.g. 4 minutes) desired to produce the relatively lowmolecular weight, mid-range vinylidene content PIB products of theinvention. These important parameters may be achieved by causing thecatalyzed reaction to take place in the tubes of a shell-and-tube heatexchanger at a flow rate which results in turbulent flow.

Many potentially valuable reactors are well known to the routineers inthe art to which the invention pertains. However, for purposes of onepreferred embodiment of the invention, the reactor may be a four-passshell-and-tube heat exchanger as shown in FIG. 1 where it is identifiedby the numeral 10. The reactor may, for example, have 80⅜-inch tubeswith a wall thickness of 0.022 inch, each thereby providing an internaltube diameter of 0.331 inch. The reactor may be three feet long and mayhave internal baffling and partitions to provide 4 passes with 20 tubesper pass. Such construction is well known in the heat exchanger andreactor arts and no further explanation is believed necessary.

In operation, the isobutylene containing feedstock enters the reactorsystem through pipe 15 which is preferably located adjacent the bottomhead 11 of reactor 10. Pipe 15 directs the feed stock into the suctionline 20 of a recirculation pump 25. The catalyst complex may be injectedinto the reactor circulation system through pipe 30 located adjacentbottom head 11 of reactor 10. It should be noted here, that inaccordance with the principles and concepts of the invention, thecatalyst complex could just as well be injected separately into thereactor, in which case a separate catalyst pump may be required.

A catalyst modifier may be added to the feedstock via pipe 16 before thefeedstock enters the reactor system. The desirable purpose of themodifier is to assist in controlling the vinylidene content of the PIBproduct. The catalyst modifier may potentially be any compoundcontaining a lone pair of electrons such as an alcohol, an ester or anamine. However, it is pointed out in this regard that if the amount ofmodifier is too great, the same may actually kill the catalyst. Thefeedstock containing the modifier enters the reactor system at thesuction line 20 of the circulation pump 25. The catalyst complexcomposition enters the reactor system via line 30 at a locationdownstream from pump 25 and adjacent the first pass as shown in FIG. 1.The catalyst complex is preferably a methanol/BF₃ complex with a molarratio of methanol to BF₃ of about 1.3:1 or less. The amount of modifieradded via line 16 may vary from 0 to about 1 mole for each mole of BF₃added as a complex via line 30.

Circulation pump 25 pushes the reaction mixture through line 35, controlvalve 40 and line 45 into the bottom head 11 of the reactor 10. A flowmeter 46 may be positioned in line 45 as shown. The reaction mixturetravels upwardly through pass 50, downwardly through pass 51, upwardlythrough pass 52 and downwardly through pass 53. As explained previously,each pass 50, 51, 52 and 53 may preferably include 20 separate tubes.For clarity, only a portion of respective single tube is illustratedschematically in each pass in FIG. 1. These tubes are identified by thereference numerals 50 a, 51 a, 52 a and 53 a. However, as discussedabove, each pass will consist of a plurality, for example 20, of theseindividual tubes, each of which extend between top head 11 and bottomhead 12 and are in fluid communication the fluids in heads 11 and 12.

It is to be noted here, that the reaction mixture should preferably becirculated through the tubes 50 a, 51 a, 52 a, 53 a of the reactor at aflow rate sufficient to obtain turbulent flow, whereby to achieveintimate intermixing between the catalyst complex and the reactants anda heat transfer coefficient appropriate to provide proper cooling. Inthis regard, the flow rate, the reaction mixture properties, thereaction conditions and the reactor configuration should be appropriateto produce a Reynolds number (Re) in the range of from about 2000 toabout 3000 and a heat transfer coefficient (U) in the range of fromabout 50 to about 150 Btu/min ft² EF in the tubes of the reactor. Suchparameters may generally be obtained when the linear flow rate of atypical reaction mixture through a tube having an internal diameter of0.331 inch is within the range of from about 6 to 9 feet per second.

The circulating reaction mixture leaves reactor 10 via suction line 20.The circulating reaction mixture is preferably maintained at steadystate equilibrium conditions so that the reactor, in essence, is aContinuous Stirred Tank Reactor (CSTR). The reactor may also be of thetype which is sometimes referred to as a loop reactor. With this system,which is only a preferred system since there are many other arrangementswhich would be apparent to those of ordinary skill in the art, the flowrate of the reactant mixture in the reactor may be adjusted andoptimized independently of feed stock introduction and product removalrates so as to achieve thorough intermixing of the catalyst complex andthe reactants and appropriate temperature control.

A product exit line 55 may preferably be provided in top head 12 at apoint which is approximately adjacent the transition zone between thethird and fourth passes. Such positioning may be desirable to avoid anypotential for loss of unreacted isobutylene. Moreover, the positioningof the exit line 55 should be appropriate to facilitate bleeding of gasfrom the reactor during startup. A coolant may desirably be circulatedon the shell side of the reactor at a rate to remove heat of reactionand maintain the desired temperature in the reactor.

The product exiting the system via line 55 should be quenchedimmediately with a material capable of killing the catalyst, such as,for example, ammonium hydroxide. Thus, any potential rearrangement ofthe polymer molecule which would shift the double bond away from thedesired terminal and beta positions is minimized. The relatively lowmolecular weight, mid-range vinylidene content PIB products of theinvention may then be directed to a work up system (not shown) wherecatalyst salts may be removed and the PIB product separated fromunreacted isobutylene and other undesirable contaminants such asdiluents, etc. These latter materials may then be recycled or divertedfor other uses employing known methodology.

With the described recirculation system, the rate of feedstockintroduction into the reaction mixture and the rate of product removalare each independent of the circulation rate. As will be appreciated bythose of ordinary skill in the art, the number of passes through thereactor and the size and configuration of the latter are simply mattersof choice. The feedstock and product withdrawal flow rates maypreferably be chosen such that the residence time of the reactionmixture within the reactor is 4 minutes or less, desirably 3 minutes orless, preferably 2 minutes or less, even more preferably 1 minute orless, and ideally less than 1 minute. From a commercial operatingviewpoint, the flow rate should be such that the residence time of thereaction mixture in the reactor is within the range of from about 45 toabout 90 seconds. In connection with the foregoing, the residence timeis defined as the total reactor system volume divided by the volumetricflow rate.

The recirculation flow rate, that is the flow rate of the reactionmixture in the system induced by the recirculation pump 25, iscontrolled, as described above, to achieve appropriate turbulence and/orheat transfer characteristics. This recirculation flow rate is often afunction of the system itself and other desired process conditions. Forthe system described above, the ratio of the recirculation flow rate tothe incoming feedstock flow rate (recycle ratio) should generally bemaintained in the range of from about 20:1 to about 50:1, desirably inthe range of from about 25:1 to about 40:1, and ideally in the range offrom about 28:1 to about 35:1. In particular, in addition to causingturbulence and providing an appropriate heat transfer coefficient, therecirculation flow rate of the reaction mixture should be sufficient tokeep the concentrations of the ingredients therein essentially constantand/or to minimize temperature gradients within the circulating reactionmixture whereby essentially isothermal conditions are established andmaintained in the reactor.

As mentioned above, the recycle ratios generally should be in the rangeof from about 20:1 to about 50:1. Higher recycle ratios increase thedegree of mixing and the reactor approaches isothermal operation leadingto narrower polymer distributions. Lower recycle ratios decrease theamount of mixing in the reactor, and as a result, there is a greaterdiscrepancy in the temperature profiles. As the recycle ratio approacheszero, the design equations for the reactor reduce to those for a plugflow reactor model. On the other hand, as the recycle ratio approachesinfinity, the modeling equations reduce to those for a CSTR. When CSTRconditions are achieved, both temperature and composition remainconstant and the composition of the product stream leaving the reactoris identical to the composition of the reaction mixture recirculating inthe reactor.

Needless to say, after equilibrium has been established, as feedstockenters the system, an equal volume of product is pushed out of thereactor loop. Under CSTR conditions, the point at which the productstream is withdrawn is independent of reactor geometry. However, the topof the third pass was chosen so any air or non-condensable species inthe reactor at start-up may conveniently be purged. Also, it ispreferred that the withdrawal point be as far as possible from the pointwhere fresh feedstock is introduced into the system just to make surethat conditions within the reactor have achieved steady-state operationand are therefore as stable as possible

The feedstock entering the system through line 15 may be any isobutylenecontaining stream such as, but not limited to, isobutylene concentrate,dehydro effluent, or a typical raff-1 stream. These materials aredescribed respectively below in Tables 1, 2 and 3.

TABLE 1 Isobutylene Concentrate Ingredient Weight % C₃s 0.00 I-butane6.41 n-butane 1.68 l-butene 1.30 I-butene 89.19 trans-2-butene 0.83cis-2-butene 0.38 1,3-butadiene 0.21

TABLE 2 Dehydro Effluent Ingredient Weight % C₃s 0.38 I-butane 43.07n-butane 1.29 l-butene 0.81 I-butene 52.58 trans-2-butene 0.98cis-2-butene 0.69 1,3-butadiene 0.20

TABLE 3 Raff-1 Ingredient Weight % C₃s 0.57 I-butane 4.42 n-butane 16.15l-butene 37.22 I-butene 30.01 trans-2-butene 8.38 cis-2-butene 2.271,3-butadiene 0.37 MTBE 0.61

For commercial and process economies, the isobutylene content of thefeedstock generally should be at least about 30 weight %, with theremainder comprising one or more non-reactive hydrocarbon, preferablyalkane, diluents.

The desired product is a relatively low molecular weight, mid-rangevinylidene content PIB product. Thus, the polyisobutylene leaving thereactor by way of line 55 should have an M_(N) which is less than about10,000. Generally speaking, the produced isobutylene should have anM_(N) within the range of from about 500 to about 5000, desirably fromabout 600 to about 4000, preferably from about 700 to about 3000, evenmore preferably from about 800 to about 2000, and ideally from about 900to about 1050. By carefully controlling the various parameters of theprocess, it is possible to produce a product wherein the M_(N) isrelatively consistent at some desired number, for example, 950 or 1000.

The polydispersity of the relatively low molecular weight, mid-rangevinylidene content PIB product may also be important. The termpolydispersity refers to the molecular weight distribution in a givenpolymer product and generally is defined as the ratio of the molecularweight of the highest molecular weight molecule to the molecular weightof the lowest molecular weight molecule. Polydispersity may becontrolled by carefully maintaining constant monomer concentrations andisothermal conditions within the reaction mixture. Generally speaking,it is desirable that the polydispersity be as low as possible in orderto diminish the content of unwanted relatively low or high molecularweight polyisobutylenes in the product and thus improve the quality ofthe latter. By following the concepts and principles of the presentinvention, it has been found that the polydispersity of the product maybe controlled at no more than about 2.0. Preferably, through the use ofthe invention, a polydispersity of no more than about 1.65 may beachieved. Even more desirably, the polydispersity may be controlled soas to be within the range of from about 1.3 to about 1.5.

The relatively low molecular weight, mid-range vinylidene content PIBproducts obtained through the use of the present invention shouldgenerally have a terminal (vinylidene) unsaturation content less thanabout 70%. That is to say, less than about 70% of the double bondsremaining in the polymerized product should be in a terminal position.Desirably, the vinylidene content of the relatively low molecularweight, mid-range vinylidene content PIB product of the invention may beless than about 60%, less than about 50%, less than about 40%, less thanabout 30%, and perhaps even as low as 20%, depending upon the needs ofthe end use application. Conversely, the beta double bond content of therelatively low molecular weight, mid-range vinylidene content PIBproduct of the invention may desirably be greater than 30%, greater than40%, greater than 50%, greater than 60%, greater than 70%, or even ashigh as 80%, again depending upon the needs of the end use application.It is to be recognized in this regard that the vinylidene content may beindirectly related to conversion rates. That is to say, the higher theconversion rate, the lower the vinylidene content. Moreover, vinylidenecontent is directly related in the same way to molecular weight.Accordingly, in each process a balance may be required between molecularweight, conversion rate, vinylidene content and beta double bondcontent.

EXAMPLE 1

Using the principles and concepts of the invention, a reactor such asthe reactor illustrated in FIG. 1, may be used to produce the relativelylow molecular weight, mid-range vinylidene content PIB product of theinvention. The feedstock may be essentially the same as that shown abovein Table 1, and the coolant circulated on the shell side of the reactormay be a mixture of 50 weight % methanol and 50 weight % water. Theinlet coolant temperature may be about 32 EF. A 1:1.3 BF₃/methanolcomplex catalyst may be used to achieve the results set forth below inTable 4.

TABLE 4 Feedstock flow rate 1.25 gpm Recirculation flow rate 35 gpmFeedstock density 5 lb/gal Reaction temperature 60 EF. Conversion 35 wt% Concentration of isobutylene in 92 wt % feedstock ΔH_(reaction) 300Btu/lb μ reaction mixture 4.0 centipoise = 0.0027 lb/ft sec Cp ofreaction mixture 0.46 Btu/lb EF. Reaction effective density 44.9 lb/ft³Thermal conductivity 0.07 Btu/hr ft EF. Total volume of reactorrecirculation 390.2 in³ system Residence time 79.82 seconds Linearvelocity inside tubes 6.52 ft/sec Reynolds number 2504.4 Surface area oftubes 23.5 ft² Heat generated 603.8 Btu/min ΔT_(lm) 66.5 EF. Heat flux25.6 Btu/min ft² U 96.1 Btu/min ft² EF.

EXAMPLE 2

Using the principles and concepts of the invention, a full scalereactor, such as the reactor 100 illustrated in FIG. 2, may also be usedto produce the relatively low molecular weight, mid-range vinylidenecontent PIB product of the invention. In this case, the reactor 100 is atwo-pass shell-and-tube heat exchanger. The reactor 100 may, forexample, have 388 0.0375-inch tubes with a wall thickness of 0.035 inch,each thereby providing an internal tube diameter of 0.305 inch. Thereactor 100 may be twelve feet long and may have internal baffling andpartitions to provide 2 passes with 194 tubes each. The passes areidentified by the reference numerals 150 and 151 in FIG. 2, and the 194tubes of each pass are represented by the single tube portions 150 a and151 a shown schematically in FIG. 2. Desirably, the product exit line155 may be provided in the bottom head 111 of reactor 100. Other thanthe number of passes, the number of tubes per pass, and the position ofthe exit line 155, the reactor 100 of FIG. 2 operates in essentially thesame manner as the reactor 10 of FIG. 1.

As in Example 1, the feedstock again may be essentially the same asshown above in Table 1, and the coolant circulated on the shell side ofthe reactor may be a mixture of 50 weight % methanol and 50 weight %water. The inlet coolant temperature may be about 32 EF. A 1:1.3BF₃/methanol complex catalyst may be used to achieve the results setforth below in Table 5.

TABLE 5 Feedstock flow rate 22 gpm Recirculation flow rate 300 gpmFeedstock density 5 lb/gal Reaction temperature 60 EF. Conversion 70 wt% Concentration of isobutylene in 89 wt % feedstock ΔH_(reaction) 300Btu/lb μ reaction mixture 4.0 centipoise = 0.0027 lb/ft sec Cp ofreaction mixture 0.46 Btu/lb EF. Reaction effective density 44.9 lb/ft³Thermal conductivity 0.07 Btu/hr ft EF. Total volume of reactorrecirculation 7794.9 in³ system Residence time 92.03 seconds Linearvelocity inside tubes 6.79 ft/sec Reynolds number 2401.7 Surface area oftubes 457.1 ft² Heat generated 20559.0 Btu/min ΔT_(lm) 26 EF. Heat flux45 Btu/min ft² U 104.3 Btu/min ft² EF. Cp coolant 0.86 Btu/lb EF.Density coolant 7.70 lb/gal Coolant flow rate 412.0 gpm ΔT coolant 8.0EF

The composition of the product thus obtained is set forth below in Table6.

TABLE 6 Crude Polyisobutylene Product Ingredient Weight % C₄ 31.5 C₈0.07 C₁₂ 0.7 C₁₆ 0.9 C₂₀ 0.7 C₂₄ 0.3 polyisobutylene 56.19 (PIB)

As mentioned above, the M_(N) of the product generally varies inverselywith the temperature of the reaction. That is to say, highertemperatures generally result in products having a lower M_(N). Toillustrate this phenomena, the reaction temperature in reactor 100 wasvaried while holding other variables constant with the results set forthbelow in Table 7.

TABLE 7 Crude Polymer Composition (including isobutane and unreactedisobutylene) Reaction Molecular Temp. Crude PIB Composition (wt %)Weight (° F.) C4 C8 C12 C16 C20 C24 PIB 350 83 19.9 5.0 16.2 11.6 5.21.6 40.6 550 75 24.4 0.4 6.2 6.4 3.5 1.6 57.5 750 72 27.9 0.2 2.8 3.22.0 0.9 63.1 950 60 31.5 0.07 0.7 0.9 0.7 0.3 65.9 2300 20 64.4 0.0040.08 0.1 0.1 0.04 35.3

1. A mid-range vinylidene content PIB polymer composition comprising PIBmolecules, wherein a first portion of said PIB molecules have alphaposition double bonds and a second portion of said PIB molecules havebeta position double bonds, wherein said first and second portionstogether include at least 90% of the PIB molecules of the composition,wherein no more than about 10% of the PIB molecules of the compositionhave tetra-substituted internal double bonds, wherein said first portioncomprises less than 70% of the PIB molecules of the composition, andwherein said composition has a polydispersity of no more than 2.0, saidPIB polymer composition characterized by having been prepared by aprocess comprising: providing a liquid feedstock comprising isobutylene;providing a catalyst composition comprising a stable complex of BF₃ anda catalyst complexing agent, wherein the ratio of complexing agent toBF₃ in said complex is no more than about 1.3:1; introducing saidfeedstock and said catalyst composition into a residual reaction mixturein a loop reactor reaction zone; recirculating the residual reactionmixture in said zone at a recirculation rate sufficient to causeintimate intermixing of the residual reaction mixture, the feedstock andthe catalyst composition to thereby present a recirculating, intimatelyintermixed reaction admixture in said reaction zone; maintaining therecirculating intimately intermixed reaction admixture in its intimatelyintermixed condition and removing heat of reaction from the reactionadmixture at a rate calculated to provide a substantially constantreaction temperature in the reaction admixture while the same isrecirculating in said reaction zone; withdrawing a product streamcomprising said mid-range vinylidene content PIB polymer composition;and controlling the introduction of said feedstock into said reactionzone and the withdrawal of said product stream from the reaction zonesuch that the residence time of the isobutylene components undergoingpolymerization in the reaction zone is no more than about 4 minutes. 2.A mid-range vinylidene content PIB polymer composition as set forth inclaim 1, wherein said reaction temperature is at least about 60 ° F.,and wherein said agent is methanol.
 3. A mid-range vinylidene contentPIB polymer composition as set forth in claim 1, wherein the ratio ofcomplexing agent to BF3 in said complex is about 1:1.
 4. A mid-rangevinylidene content PIB polymer composition having an alpha positiondouble bond content that is less than 70% of the total double bondcontent of the composition and a polydispersity of no more than 2.0,said composition characterized by having been produced by a processcomprising: providing a feedstock comprising isobutylene; providing acatalyst composition comprising a complex of BF₃ and a complexing agenttherefor; introducing said feedstock and said catalyst composition intoa residual reaction mixture in a reaction zone; intimately intermixingsaid residual reaction mixture, said feedstock and said catalystcomposition to present an intimately intermixed reaction admixture insaid reaction zone; maintaining the intimately intermixed reactionadmixture in its intimately intermixed condition and keeping it at atemperature of at least about 0 ° C. while the same is in said reactionzone, to thereby cause the isobutylene therein to undergo polymerizationto form said polyisobutylene; manipulating the ratio of BF₃ tocomplexing agent in the catalyst composition so as to adjust thevinylidene content of the PIB polymer composition; withdrawing a productstream comprising polyisobutylene having an alpha plus beta isomercontent of at least about 90% from said reaction zone; and controllingthe introduction of said feedstock into said reaction zone and thewithdrawal of said product stream from the reaction zone such that theresidence time of the isobutylene undergoing polymerization in thereaction zone is no greater than about 4 minutes.